Circuit breaker and overload protective device



Sept. 19, 1944. w. E. sTlLwELL, JR y 2,358,357

CIRCUIT BREAKER A'ND OVERLOAD PROTECTIVE DEVICE Filed May 1, 1942 2Sheets-Sheet l www "mn o if, ,Jffmfummfffmwwm@ l IE 62a' i :O

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ga ORNY Sept 19, 1944 w. E. sTILwELL, JR 2,358,357

CIRCUIT BREAKER AND OVERLOAD PROTECTIVE DEVICE Filed May l', 1942 2Sheets-Shea?. 2

2o v. INVENTOR Willi ESilweLJ-n LOAD Patented Sept. 19,1944

crncurr Bamm AND ovEnLoan raorEc'nvE nEvIcE William E. Stilwell, Jr.,Cincinnati, Ohio, assignor to John B. Pierce Foundation, New York, N.Y., a corporation of New York Application May 1, 1942, Serial No.441,383

(Cl. 20G-88) 14 Claims.

This invention relates to circuit breakers, and particularly to circuitbreakers adapted for remote control, and embodying overload protectionmeans.

Among the objectives of the invention are: K

To provide a circuit breaker, as aforesaid. which is exceedingly compactin form and lightl in weight, thereby rendering the same applicable toinstallations where size and weight are of importance, such as inaircraft;

To provide a circuit breaker which is reliable in operation, andinexpensive in construction;

To provide a circuit breaker of the overload .protection type, whichwill withstand extreme conditions of vibration and violent positionalchange without change in its operating characteristics;

To provide a circuit breaker which may be contained in a sealed,gas-proof and explosionproof housing; To provide a circuit breakerhaving "trip-free characteristics;

To provide a circuit breaker having overload protection, in which theoverload cut-out point may be changed by simple substitution of elementswithout change in the circuit breaker mechanism, per se; and

To provide a circuit breaker having overload protection, in which, afterthe circuit has automatically been broken imder the influence otoverload, it is necessary for the circuit breaker to be thrown to oilposition before the electric circuit can again be closed.

The circuit breaker is adapted for remote control; such remote controlmay be actuated mechanically, as by a Bowden wire or equivalent meansfor transmitting mechanical movement, but preferably, the remote controlcircuit embodies magnetic actuating means. It is desirable for operatethe magnetic system on low voltage, to make possible the use of smallsize conductors, lightly insulated, for the remote control circuit. Whenemployed with low voltage control circuits, a suitable transformer maybe incorporated in the circuit breaker housing. r, if desired, atransformer may be connected into the remote control circuit at alocation remote from the circuit breaker.

In aircraft, boats, or other installations where low voltage isavailable for lighting or otherservice, the remote control may beoperated directly by said low voltage service; usually, such low voltagecircuits are direct current.

A preferred form of circuit breaker embodying the present invention,therefore, includes a pair of magnetic coils, centrally arranged withrespect to which is an armature system, movable toward one or the otherof the coils, depending upon the energization thereof. The armaturesystem includes a magnetically responsive member extending from each endof which, and secured thereto in the line of the axis thereof, is ashaft; to each shaft, at its end, is secured a suitable toggle spring.

0ne of said toggle springs, hereinafter referred to as the throw spring,operates under an initial impulse engendered by magnetic force, to movethe armature toward or away from the electric contacts of the loadcircuit depending upon which of the coils is energized, and to carrysuch armature through the full extent of its permitted travel, eventhough the magnetic coil Spring.

The load-line contacts are carried by bimetallic members through whichthe load current passes. Under the influence of an overload condition,-the bimetallic elementsheat, warp, and exert a substantial pressure on'the "contact spring. Upon the attainment of suitable pressure by thewarping of the bimetallic members, the equilibrium of the "contactspring is overcome, and'it will reverse its position, thereby mappingthe contacts carried thereby, out of engagement with the load-linecontacts.

Desirably the "contact toggle spring is of a. double equilibrium type,that is, it will not automatically return to circuit closing positionafter the interruption of the load circuit has permitted the bimetallicelements to cool to their initial position and hence no longer exertpressure on said toggle spring.

It is a feature of the invention, also, that the "throw" spring isstronger than the contact spring, whereupon the pressure exerted uponthe contact spring by the bimetallic elements, and the reaction of saidspring under the influence thereof, will not cause the "throw spring toreverse its position.

To reclose the circuit after it has opened under the iniluenceofoverload, it is necessary for the operator to energize the oiPniagneticcoil to move'the armature. The "contact spring is drawn thereby intoforcible engagement with suitable abutments, and the pressure exertedagainst the contact spring by such abutments, causes the contact springagain to reverse its position to resume itsnormal circiut closingposition. However, as the entire apparatus is then in E position, it isnecessary to close the on circuit to again move Athe armature and bringthe contact spring into circuit closing engagement with the loadcontacts.

A second form of invention which retains many of the favorable operatingcharacteristics of the double-magnet type previously discussed, mayinclude -a single electromagnet for moving the contacts into circuitclosing position and retaining them in such position against thereactive eilort of a single equilibrium point toggle spring biased toreturn the movable contacts to open circuit position when the magnetcoil is deenergized.

A feature of overload protective circuit breakers embodying thlnventionresides in mounting the birnetalllc overload elements on a removable capor plate, whereby precisely the same actu- 'ating mechanism may beemployed with overload elements of any desired degree of overloadactuation, merely by using in connection with the standard mechanism acap or plate having appropriate overload elements.

Other features and advantages will hereinafter appear. l

In the accompanying drawings: l

Fig. 1 is a perspective of a completely housed circuit breakerembodyingthe present invention;

Fig. 2 is an enlarged section taken through 2-2 of Fig. 1, illustrating'the circuit breaker in A circuit closing position; I i Fig. 3 ls apartial section similar to Flg.2, illus trating the circuit breakerimmediately after the ywarping of the bimetallic overload members hasthrown the contact. toggle spring into circuit breaking position, thethrow toggle spring and armature system of the circuit breaker remainingin circuit closing position;

Fig. 4 is a partial section similar to Fig. 3, but showing the circuitbreaker in normal open circuit posltion;

Fig. 5 is a'partial plan view of the closure member of the circuitbreaker housing, taken from the underside to show the disposition of thebimetallic overload elements and contacts thereof;

Fig. 6 is a. fragmentary plan view of the circuit breaker with theclosure member removed;

Fig. 7 is a, plan view of a preferred form of contact toggle spring withcontact structure thereon: Fig. 8 is a plan view of a preferred form ofthrow toggle spring; Y v

Fig. 9 shows a typical wiring diagram for; low voltage remote control ofthe circuit breaker of Fig. 2;

ing a magnetically operated switch mechanism and coordinatedtransformer, has the overall physical dimensions enabling it to beinstalled in a standard 1%"by 35/3" outlet box.

'Ihe housing comprises a body 2| and closure 22 therefor, completelyencasing the operative parts of the apparatus, to render the same immunefrom dust, chemical fumes, gases, or thelike, and adapting it for useunder conditions where explosive gases may be present, as in submarines,mines, or chemical manufacturing plants. A plurality of screws 'may be,employed a to maintain a tight interassembly of body and closure, and asuitable gasket (not shown) may be used to insure complete airtightness. Desirably, the body andA closure may be molded from suitableplastics, suchsas Bakelitek or equivalent.

The closure 22 is formed with a ange 23 deiining an annular recess 2liat an end of the closure. At the base of said recess there is a4 sheet25 of asbestos or equivalent having suitable re-proof and heatinsulation qualities.

Referring to Fig. 5, a plurality, illustratively two, of load-linecontact members 2B, 26, are positioned upon the sheet 25, and normally,that is, under normal load conditions, lie dat against said sheet, asshown in Fig. 2. Each of thecontact members 23 is secured at its end tothe closure .22, as by the studs 21, which pass through the closure 22to form binding posts or the like for the attachment of the conductors0f the load circuit.

At the free end of each of the contact members 26 there is a contact 28,desirably a. button or stud of silver or other material possessing highconductive qualities and resistance to pitting or corrosion under theinuence of an electric arc.

I'he contact members 26 are bimetallic', in that they are formed fromlaminations of metals having different coeicients of expansion, such assteel and copper, or-other suitable combinations known in the art. Sothat the contact members 2E will warp away from the sheet 25 under theinuence of heat, the metal having the higher coemcientfof expansionfaces said sheet.

As previously stated, said bimetallic members 26 are conductor elementsof the load circuit, and the contacts 28 thereof are engageable, underconditions of operation of the invention, by a contact structure whichcompletes the circuit therebetween. A

Desirably, the said contact structure is brought into and out of circuitclosing engagement with the contacts 28 of the contact members 26 byelectromagnetic means, such method of operation lending itself to remotecontrol whereby a simple push button or the like' may be employed toclose the operating circuit.

The electromagnetic operator for closing and opening the electric loadcircuit comprises a pair of magnet coils 3G, Si, would upcn suitablespool construction embodying steel caps 32, 32a, with central wallstructures 33, 33a acting as poles for Axially msitioned and secured tosaid core 3d vat each end thereof, and passing through an openingprovided in the stop members 32, 33a

are rods Sii, Si?.

When magnetic coil t-'hereinafter called the on' coil-is energized, Athearmature system,v

comprising the core 3d andtherewith associated rods is drawn in thedirection of the contacts 2l to close the load circuit, whereas when the"oiT coil 3l is energized, the amature system will move in reversedirection, to break the load circuit.

To carry the armature system through its full travel with but amomentary energization of the magnet coil, and with a snap motion, thereis employed, in operative association with rod 3l, a toggle spring Il.

Improved operating characteristics result from' 10 42, the dished rim 4ihaving a permanent set,

whereas the legs 42 have no permanent set. In such construction, thelegs I2 have a curvature tangential to the rim,.and are maintained inbowed elastic tension by the permanent set of rim 4i. An-importantcharacteristic of such a toggle spring is that a force-induced movementof approximately twenty-live (25) Per cent of the total throw of thespring causes the spring to throw through its full travel.

By a suitableproportion of the thickness of the rim and the depth towhich the rim is dished, the toggle spring may have either one or twopositions of stable equilibrium; that is, the toggle spring may be suchthat when it is vdeflected to a reverse curvature, it will return to itsoriginal curvature when the defiecting pressure is released or, as adouble equilibrium spring, the toggle spring will remain inthe curvatureto which it has snapped.

In the instant embodiment of the invention, it is preferable to employ adouble equilibrium toggle spring for the member 48.

As shown in Fig. 8, the legs 42 join at a circular portion at thegeometric center of the spring; at the center of such hub, is a holesuitable to receive the rod 3l. The rod may be secured to the spring 40by means including the washers 43, 44; and the rod 31 may either beriveted over said washer M, or the end of the rod may be threaded toreceive lock nuts (not shown) to sey cure the rod 3l to the spring I0. Y

The spring 40 may be relatively loosely supported about its periphery ina suitable shoulder or kerf I6 formed in the housing 2l; the peripheralcorner oi the coil spool 32a serves to secure the toggle spring M inposition while permitting unrestrained flexing thereof.

Io compensate for possible inaccuracies resulting from the molding ofthe closure 22, and to permit said closure to maintain the coils 36, 3i,in correct, iixed, position, a metal ring 22o is interposed betweenang'ex and coil cap 32. i

The contact toggle' spring, 66,' is mounted on the rod 36 so `as toprovide a limited swivel acltion about theend of the rod. Said togglespring 50 preferably also has a double equilibrium characterlstic, andmay be otherwise similar to the toggle spring 46.

Mounted on spring 50, to close circuit across the load contact buttons28, 28, is an inflexible ring deslrably a dished ring of silver, theouter edge of which is reversed upon itself to provide opposed rimsbetween which the spring 5B may be loosely held about its rim. The loosemounting of ring 5I on spring 5II renders it free to rotate about spring50, and the full periphery of the ring 5| is available as contactsurface, 'la

thereby equalizing wear, and lengthing its operating life.

Referring now to Fig. 9, the circuit breaker is shown as wired in a voltpower circuit with a transformer T used to reduce the voltage of saidcircuit suitably for the control circuit, preferably to 24 volts.- Inthe control circuit, dignated C, are any desired number of push-buttonswitches S. The push-button switches S are of double throw type; thecentral pole of the switch is common toboth magnetic coils, and throw ofthe switch in one position energizes the on coil 30 whereas the otherswitch position energizes the oit coil 3i.

With the oi coil energized, the circuit breaker is in the 4 position;each of the toggle springs 4B and l is in a concave shape, as viewed insaid figure. Upon energizing the on coil 3l, magnetic core 34 andassociated shafts 36, 3l are drawn toward the closure 22, whereuponafter a short movement of the armature system, the spring 46 snaps intothe Fig. 2 position, and contact ring 5i is brought sharply into contactwith the contacts 28 on the members 26. Spring 6l, however, retains itsinitial position oi' stable equilibrium. Desirably, the ring 5l engagesthe contacts 28 before the spring 4B has attained full throw, whereuponthe unexpended energy of spring Il! maintains the contact ring Siresiliently in engagement with said contacts. Spring 5l should be ofsuch stiffness that it will remain in its initial position of stableequilibrium under the impact force of the engagement of the ring 6I withthe contacts, and under the residual or unexpended energy of spring 4D.

Under overload, bimetallic members 26 are subjected to the heatingeffect of the overload, and the unequal expansion of the laminations ofsaid members, warps them away from base plate 25, to exert an angularlydirected pressure upon the ring 6I, and-hence upon the toggle spring 50associated therewith. If members 28 warp unequally, the self-adjustmentof spring 50 permits its inclination toward that contact 28 having the fleast movement, maintaining contact with each contact 28 until the throwpoint of spring 5U is reached. The angular pressure exerted by contacts26 against ring 5| may enforce brief angular rotation thereof.

When the overload persists, pressure of members 26 against toggle spring5U steadily increases, until toggle spring 50 is snapped from itsconcave position shown in Fig. 2, to its convex position shown in Fig.3. In other words, the spring 6l will assume its second position oistable equilibrium. The throw of the spring 5I! to its new positionmoves the ring 5I completely out oi.' engagement with the contactbuttons 28, thereby immediately breaking the circuit. In thebroken-circuit position oi vthe spring 60, it will be noted that theinner surface of the contact ring 6I bears against the coil cap 32.

The electric circuit having been broken, the contact members 26 will.cool and resume their normally nat position upon the base plate 25.

The relation of comparative strengths of the springs Il and 50 is suchthat the spring l0 will remain in its convex or closed circuit positionunder the iniluence of pressure of the contact members 26 against thespring 50.

Spring l0 and associated armature assembly remains in circuit closingposition; but because the spring 5D is of a double equilibrium type, itwill remain .in open circuit position, with the edges of the ring 5| incontact with the coil cap 32. The operator, to return the circuitbreaker to v a status wherein the load circuit lmay again b'e closedmust first venergize the oil coil Il, to draw the magnetic armaturesystem into the "ofP position. I

The movement oi the armature system returns the spring 50 to itsoriginal position, for it isrecalled that said spring 50, or the rimofthe ring 5I associated therewith, bears against the coil cap 32, and thereaction pressure against said rim snaps the spring 50 to its initiallyconcave, i. e., circuit closing shape. l.

Upon energizing the on coil 3U, therefore, the amature system andtherewith associated contact ring 5| resumes the closed circuitposition.

Under certain load conditions, spring 50 may be utilized per se as acontact structure without thereon orriveted thereto, for cooperationwith` the 'contacts 28 of the members 26. If such construction isemployed, any suitable means may be 'taken to prevent rotation of thespring 50 with respect to the contacts 28 to insure a satisfactorycontact upon closing the circuit.

sure upon the contact spring 10. When. said bimetallic members havewarped suiiiciently, the contact spring is snapped into its reverseposition of stable equilibrium, thereby breaking Fig. 10 illustrates, invertical section, an embodiment of the invention wherein a singlemagnetic coil is employed to close the circuit and to 4maintain theclosed circuit status. Pursuant to this form of the invention, the throwspring 60 has but a single point of stable equilibrium;

that is, as soon as the pressure exerted on said spring to effect itsoverthrow Ais released, the

'spring will immediately revert to its original position. The contactspring 'Hi is a 'double equilibrium spring such as the spring 50previously described.

As shown in Fig. 10, the single,magnetic coil 80 is contained within asuitable housing. -An amature system includesa core 8i, to which aresecured shafts 82, 83. Shaft B2 carries the double equilibrium contactspring 10, said spring having suitable contact means 1i, il thereon. Atits end, shaft 83 is secured to the single equilibrium spring 60, thelatter being normally biased to circuit opening position, as shown infull line in Fig. 10. Spring 60 is freely held about its periphery in akerf in housing element Bi, as

dot-dash line, and the contacts 1i of the contactv spring l0 are broughtinto circuit closing position against the load contacts Sl, 90. So longas the.

control circuit is kept closed, the continuing circuit'inclosedposition, against the urging of the single equilibrium spring I0 toreturn'the armature assembly and contact spring 18 to open circuitposition.

In a circumstance of overload m the load-circuit. the bimetallic members92, l2 warpin prothe load circuit. Because the spring 10 has twopositions of stable equilibrium, said spring will not again reverseitself when the cooling of the bimetallic members 92, 92 has returnedthem to their original position against the base 93.

The position assumed by the contact spring 10 after it has been snappedopen under overload is with its periphery. against, or closely adjacent,the housing cap |00, as shown bythe dotted line in Fig. 10. -In suchposition of spring 10, the contacts thereof cannot be 'brought intoengagement with contacts 90. In order to restore the contact spring 10to a position permitting subsequent reclosing of the load circuit, theoperator must open the control circuit; that is, he must deenergize themagnet 80, whereupon the single equilibrium spring 60 reverts to itsoriginal, i. e., open circuit, position, moving the armature system inthe direction of the housing cap |00. Such movement of thearmature-system exerts a pressure upon said spring 10 sufilcient toreverse its position, wherein it is again in position to close thecircuit across the contacts 90, 9D. However, the entire circuit breakersystem is then in open circuit position, and the control circuit C mustagain be closed to energize the magnet 8l! to reclose the load circuit.I i

To minimize the current required for magnetically holding the loadcontacts in closed circuit position, it is advantageous to interpose aisdeenergized, the contacts 62 are in engagemagnetic force of the magnet80 holds the load ment with contacts 63, and because of the high valueof resistance R, with respect to the resistance of the spring 60, theresistance Ris shunted out of the control circuit. At the instant oiclosing push button P, 'the path of current in said control circuit isthrough magnet coil 8B, and the spring system, including contacts 62,63. The magnet 80 pulls the armature system, as aforesaid, and as thespring 60 imparts a snap action to the movement of the system, thearmature system and spring 80 move practically in coordination. Justprior to the stage of throw ol' spring 60, the contacts 6l, 82, breakwith the contacts 83, 84. respectively, and the current path of thecontrol circuit is through resistance R. The introduction ofthe'additional resistance into the control circuit, following Ohms law,reduces the amperage flowing through the control circuit, and thecircuit breaker is magnetically held in, closed circuit position withsubstantially less expenditure of current'.

The operating'structure of the circuit breaker, i. e., the magnetic coilor coils. toggle springs and movable contact, may be used withbimetallic contact members 2l or 02 oivany overload characteristic. Thismaterially simpliiies manufacturing and stocking; for when filling -anorder l for a circuit breaker to operate under deilnite portion to thedegree o! overload, exerting presloverload ratings, it is only'necessaryto select a closure 2 2 with appropriate elements 2t therein, in theFig. 2 embodiment or plate 93 and elements I2 of the Fig. 10 embodiment,whereupon said structure may be used with the standard housing andoperang structure.

As shown in Fig. 2, transformer T may be tion-proof and fully trip-freeoperation.

The toggle spring throws the amature system with such speed that thearmature system may be very light in Weight. The permissible weightreduction of the movable armature sysgization of one of saidelectromagnets may exert pressure on said second snap spring to throw itto position for circuit closing while simultaneously moving it away fromsaid first-named contacts to maintain the open status of said loadcircuit.

2. A remote control circuit breaker and overload protective devicecomprising' a base, electric contacts supported on .said base, electrictem and stable equilibrium of the toggle spring make it a practicalimpossibility to throw the armature system and therewith associatedcontact spring by vibrating or shaking the circuit breaker, for theinertia of the armature system is so small in relation to the stabilityof the toggle spring that an amount of momentum suicient to throw saidspring could not be generated by any vibration condition which could beexperienced under operating conditions.

The circuit breaker is trip-free in operation because of the stableequilibrium of the contact spring and its property of remaining in opencircuit position after the overload has caused its throw to suchposition The operator cannot restrain the circuit breaker from throwingto open circuit position; nor can he return the circuit breaker toclosed circuit status without first throwing the circuit breaker to oposition to move the contact toggle spring into its potentially closedcircuit status.

Whereas I have described my invention' by reference to specificformsthereof, it will be understood that many changes and modiiicay tions maybe made provided they do not depart from the scope of the claims.

I claim:

1. In a remote control circuit breaker and overload protective device,the combination with a base, a plurality of bimetallic strips mountedthereon for connection into an electric circuit, each of said bimetallicstrips being secured at one end to said base and having contact means attheir respective freel ends, of a pair of solenoid coils adapted to beindividually energized in a remote control circuit. an armature systemmovable toward one or the other of said magnetic coils according to-theenergization thereof, a snap spring secured to said armature system tomaintain the same in either of its extremes of travel, a second snapspring secured to said armature system, electric contact means carriedby said second snap spring and movable into or out of circuit closingassociation with said first-named contacts according to the movement'ofsaid armature system; said second snap spring having two positions ofstable equilibrium, in only one of which positions may the contactscarried thereby engage with said firstnamed contacts; said bimetallicstrips, when subjected to a condition of electrical overload, exertingpressure on said second snap spring to throw the same into its otherposition of stable equilibrium upon the attainment of a predetermined.overload condition, thereby causing said snap spring to carry its saidcontacts out ci circuit closing association; and means whereby movementof said armature system by ener- -contacts movable into or out ofcircuit closing engagement with said rst-named contacts to complete thecircuit thereacross, electromagnetic means for moving said movablecontacts into or out of circuit closing position, said means including apair of electromagnets, an armature system associated therewith andmovable toward one or the other of said magnets according to theenergization thereof, a snap spring associated with said armature systemto hold, the same at either of its extremes of move-V not be broughtinto engagement with said contacts, and thermostatic means associatedwith said ilrst-named contacts and movable toward said second named snapspring under predetermined conditions of overload of the load circuit tosnap vthe said spring into its open circuit position of stableequilibrium to thereby move its said contacts out of engagement withsaid first-named contacts. Y

3. A remote control circuit braker and overload protective device as setforth in claim l, wherein said rst named snap spring has two positions.of stable equilibrium, and wherein said snap spring will remain in aposition of stable equilibrium against the pressure of said bimetallicstrips and the reaction of said second named snap spring thereby.

4. A remote control circuit breaker and overload protective device,comprising a base, electric contacts positioned on said base, circuitclosing contacts movable with respect to said contacts to make or breakelectrical connection thereacross, electromagnetic means for so movingsaid circuit closing contacts, a snap spring for resiliently holdingsaid circuit closing contacts in either of their extremes of movement, asecond snap spring carrying said circuit closing contacts, said secondsnap spring having two positions of stable equilibrium, in only one ofwhich positions the circuit closing contacts may be moved intoengagement with said rstnamed contacts for closing a circuitthereacross, means whereby said electromagnetic means may cause saidsecond snap spring to assume its potentially circuit closing position,and thermostatic means operating upon said second snap spring when thecontacts thereof are in closed circuit position to move said snap springand therewith associated contacts'into open circuit position uponattainment of a predetermined temperature in said thermostatic means.

5. A remote control circuit breaker and overload protective device,comprising a base, contacts positioned on said base, circuit closingcontacts movable with respect to v'said first-named contacts to make orbreak electrical connection thereacross, electromagnetic means for somoving said circuit closing contacts, a snap spring for resiiientiyholding said circuit closing contacts in either of their extremes ofmovement, a

second snap spring carrying said circuit closing contacts, said secondsnap spring having two positions of stable equilibrium, in only one ofvi which positions the circuit closing contacts may sociated contactsinto open circuit position upon attainment of a predeterminedtemperature in said thermostatic means. I

6. A remote control circuit breaker and overload' protective device asset forth in claim 4, in

which said thermostatic means are bimetallic elements secured at one endto said base and said assess? contact between said rst-named contactsand said movable contacts under predetermined temrst-named contacts arecarried by the free end of said bimetallic elements.

7. A remote control circuit breaker and overload protective device asset forth in claim 4 in which the circuit closing contacts comprise aring of electrically conductive material.

8. A remote control circuit breaker and overload protective device asset forth in claim 4, in which the snap spring carrying said circuitclosing contacts comprises a dished spring member supported only at itscenter.

9. A remote control circuit breaker and overload protective device as set forth in claim 4, in which the snap spring carrying Said circuitclosing contacts comprises a dished spring member supported only at itscenter and the contact carried thereby comprises a ring of electricallycons ductive material loosely secured to said snap spring about itsperiphery. Y

10. A remote control circuit breaker and overload protective device,comprising a base, con tacts positioned on said base. contacts movableperature conditions.

il. An electric circuit breaker as set forth in claim 14, wherein saidsnap spring and therewith associated contacts remain in open circuitposition after the circuit 'has been broken.

Y 12. A circuit breaker, including contacts for connection into anelectric circuit, a rod movable toward or away from said contacts, meansfor moving said rod, a toggle spring operatively assoi ciated with saidrod and movable thereby, said toggle spring having two positions ofrepose, contact means carried by said toggle spring and arranged thereonin such manner 'that in one posi.. tion of repose of said toggle 'springthe contact means may be brought into or out of engagement with saidcontacts upon movement of said rod but in a second position of repose ofsaid toggle spring movement of the rod is ineective to bring. thecontact means intov engagement with the contacts, and means responsiveto a conditionof overload in the electric circuit to move said togglespring into its' said second position of repose.

13. A remote control circuit breaker and overload protective device asset forth in claim 4, in which the snap spring carrying said circuitclosing contacts comprises a dished spring member swivelly supported atits center and the circuit closing contact comprises a ring ofelectrically conductive material free to rotate about the snap springsupporting means.

4o movable rod and a snap spring supported only by with respect to saidfirst-named contacts to make movable contacts in either of theirextremes of movement, a second snap spring assooiatedwith said movablecontacts, and means responsive to the temperature of said mst-namedcontacts and operative upon said second snap spring to break said rodand secured thereto at its center, said snap spring carrying saidmovable contacts, and means associated with said nxed contacts formoving the said movable contactsv out of engage-- ment therewith in thecircumstance of overload at said fixed contacts, said means including aplurality of thermally responsive members adapted to exert pressureagainst'the outer edges of said snap spring atsubstantially-diametrically opposite positions thereof as thetemperature of said thermally responsive means increases, underoverload, to a predetermined point.

` WILLIAM E. STILWELL, Je.

